The present invention relates to turbine nozzles of steam turbines and, more particularly, to sealing of steam turbine nozzle hook leakages using a braided rope seal.
Within a steam turbine, there are static nozzles (airfoils) that turn the flow into the buckets, which in turn extract work from the flow medium. In a reaction-style turbine design, these nozzles are assembled into an inner casing (shell). The nozzles are slid into a circumferential hook as individual or “ganged” nozzle segments. A leakage circuit exists around the nozzle to stator hook. This leakage bypasses the nozzle, and therefore the flow is not “turned” or accelerated through the nozzle throat. Both losses result in reduced stage efficiency and unaccounted for leakage to the system. Depending upon the machine intolerances, surface finish and nozzle loading, this leakage may be highly variable.